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Original question:

LP2998: voltage accuracy

LP2998: voltage accuracy

K.Hamamoto
Guru 12155 points
Part Number: LP2998

Hi

I have an additional question.

Regarding VREF accuracy, at JEDEC standard the accuracy is defined +/-2%. However the accuracy of LP2998 is exceed that standard.

LP2998 ; VREF_max = 0.937V@VDDQ=1.8V and VREF_max = 0.986V@VDDQ=1.9V.

JEDEC standard ; VREF_max = 0.51*VDDQ @VDDQ=1.7~1.9V.

(e.g. if VDDQ=1.9V, VREF_max=0.969V.)

So that, I think LP2998 does not meet JEDEC standard. Is my understanding correct?

Best Regards,

Koji Hamamoto

  • 0
    TI__Mastermind 24075 points

    Hi Koji,

    I believe the VREF tolerance spec is tested with +/-10uA current.

    The typical output impedance of VREF pin is 2.5kohm.

    Usually the VREF current drawn by DIMM is very small, only 1 or 2 uA.

    When VDDQ=1.9V, with 2uA sink current, the VREF_max=0.95V+(2.5kohm*2uA)=0.955V.

    It should be fine to use LP2998 in DDR2 application.

    Thanks

    Qian